• 한국생산제조학회지
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• 제6권4호
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• pp.39-45
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• 1997

Shadow moire topography has been used as a noncontact method for measuring the 3-D shapes of objects. The moire fringes are results from the superposition of a master grating and its shadow projected on the surface of an object. But in case of the classical shadow moire method, in general, the resolution is a few tenths of millimeter. It is difficult to use a phase -shifting method in shadow moire because it is impossible to obtain uniform phase shifts on the whole field. But in this study , We introduce a phase-shifting method to improve the resolution of the classical shadow moire method. This method is based on the fact that if the depth of object is much less than the distance between the observer and the master grating, the phase shifts are almost uniform on the whole field area. Finally, we applied this new phase-shifting method to the measurement of the 3-D shape of a coin.

• Journal of the Optical Society of Korea
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• 제10권4호
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• pp.178-183
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• 2006

An in-line phase-shifting digital holographic microscopy system was constructed by inserting a conventional microscope in the object arm of a Mach-Zehnder interferometer. It was used to measure the three dimensional shape of a micro Fresnel lens. It was also shown that both the lateral and the axial resolutions of the in-line phase-shifting system using a self-calibration algorithm were superior to those of the best off-axis system.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.281-287
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• 2008

An acousto-optic tunable filter based 3-D micro surface profile measurement using an equally spaced 5 spectral phase shifting is described. The 5-bucket spectral phase shifting method is compared with a Fourier-transform method in the spectral domain. It can provide a fast measurement capability while maintaining high accuracy since it needs only 5 pieces of spectrally phase shifted imaging data and a simple calculation in comparison with the Fourier transform method that requires full wavelength scanning data and relatively complicated computation. The 3-D profile data of micro objects can be obtained in a few seconds with an accuracy of ${\sim}10nm$. The 3-D profile method also has an inherent benefit in terms of being speckle-free in measuring diffuse micro objects by employing an incoherent light source. Those simplicity and practical applicability is expected to have diverse applications in 3-D micro profilometry such as semiconductors and micro-biology.

• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.983-990
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• 2022

In this paper, we implemented a hierarchical encryption system using two-step phase-shifting digital holography(PSDH) technology based on XOR and scramble operations. The proposed encryption system is a system that authenticates access through the issuance of an encryption key for access to individual laboratories, department offices, and universities. In the encryption process, we proposed a double encryption method using XOR and scramble operation with digital technology and two-step phase-shifting digital holography with optical technology. In the two-step PSDH process, an new method of determining the reference wave intensity without measuring it by using random common object image gererated from digital encryption process was also proposed. In the decryption process, the process is performed in the reverse order of encryption process. And only when the various key information used in the encryption process is correct, the encrypted information can be decrypted, so that the user can access the desired place. That is, there is a feature that can hierarchically control the space that can be accessed according to the type of key issued in the proposed encryption system. Through the computer simulation, the feasibility of the proposed hierarchical encryption system was confirmed.

• 비파괴검사학회지
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• 제25권2호
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• pp.67-73
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• 2005

레이저 간섭계를 이용하여 수백 나노미터 정도의 박막 두께를 측정하였다. 마흐-젠더 간섭계로 실험장치를 구성하고 위상이동법을 통해 박막을 투과할 때 생기는 위상지연을 측정하였다. 광휘 상관 모델을 적용하여 위상 이동법의 단점인 위상이동 오차가 보정된 위상도를 측정하였다. 기존에는 고려되지 않았던 공간적 위상 이동오차를 보정하기 위하여 최소자승법을 이용하여 위상 기준면을 추정하였다. 이 방법으로 미세한 위상지연을 측정해야 하는 100nm $Si_3N_4$ 박막시료의 두께를 5nm의 정밀도로 측정할 수 있었다.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2457-2462
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• 2011

생산방식의 변화에 따라 3차원 형상을 신속하고 정확하게 측정하는 것이 중요해졌다. 가장 훌륭한 비접촉 3차원 측정방법인 모아레 방법 중 잡음신호를 효과적으로 제거할 수 있는 위상천이 방법을 구현함에 있어 DMD를 이용하여 격자를 생성하고 이송하는 효과를 발생하도록 하였다. 컴퓨터에서 격자를 이송하고 위상천이를 발생하므로 기계적 이송으로 인한 잡음신호의 발생 가능성을 배제할 수 있으며 광학렌즈와의 적절한 조합을 통해 쉽게 분해능을 변화하며 3차원 정보 획득이 가능하다. 근본적인 $2\pi$ 모호성문제를 극복하기 위하여 2차원 위상정력을 실시하였다. 이 방법을 적용하여 3차원 형상의 측정을 수행하였다.

• 한국정밀공학회지
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• 제18권7호
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• pp.149-154
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• 2001

This study discusses a non-contact optical technique, electronic speckle pattern interferometry(ESPI), that is well suited for a deformation measurement of structure. Phase shifting method and unwrapping method have used to make deformation quantitative widely. In this paper, a previous numerical formula for phase shifting method is reconstructed in addition to least square fitting method to improve sensitivity and phase unwrapping based on vertical-horizontal scanning method is applied to analyze in-plane and out-of-plane deformation quantitatively.

• 한국정밀공학회지
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• 제25권1호
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• pp.85-91
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• 2008

White light scanning interferometry has gotten a firm position in 3D surface profile measuring field. Recently, the LCD industry gave a chance for this technology to enter into real industry fields. It is known that white-light phase-shifting algorithm give a best resolution compare to other algorithms, but there are some problems to be resolved. One of them is 300nm jump in height profile, called bat-wing effect. The main reason of this problem is an ambiguity of phase-peak detection algorithm, and some solution has been proposed, but it didn't work perfectly. In this paper, I will show the cases when these effects are occurred, and these height discrepancies will be almost disappeared when broad-band illuminators are used.

• Current Optics and Photonics
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• 제2권5호
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• pp.474-481
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• 2018

We propose a polarization phase-shifting technique to investigate the thickness of $Ta_2O_5$ thin films deposited on BK7 substrates, using a modified Sagnac interferometer. Incident light is split by a polarizing beam splitter into two orthogonal linearly polarized beams traveling in opposite directions, and a quarter-wave plate is inserted into the common path to create an unbalanced phase condition. The linearly polarized light beams are transformed into two circularly polarized beams by transmission through a quarter-wave plate placed at the output of the interferometer. The proposed setup, therefore, yields rotating polarized light that can be used to extract a relative phase via the self-reference system. A thin-film sample inserted into the cyclic path modifies the output signal, in terms of the phase retardation. This technique utilizes three phase-shifted intensities to evaluate the phase retardation via simple signal processing, without manual adjustment of the output polarizer, which subsequently allows the thin film's thickness to be determined. Experimental results show that the thicknesses obtained from the proposed setup are in good agreement with those acquired by a field-emission scanning electron microscope and a spectroscopic ellipsometer. Thus, the proposed interferometric arrangement can be utilized reliably for non-contact thickness measurements of transparent thin films and characterization of optical devices.

• 조명전기설비학회논문지
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• 제27권1호
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• pp.109-112
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• 2013

It is well known that the maximum torque of a 3-phase induction motor does not vary as the resistance of rotor varies by proportional shifting. However, proportional shifting is derived using simplified equivalent circuit of induction motor. Therefore, there are some errors in the torque characteristics shown in the text book. This paper presents the torque characteristics using not simplified equivalent circuit but equivalent circuit. Errors produced by simplified equivalent circuit are presented.